Hemophilia is sometimes called “the royal disease” because of its presence among members of European royal families in the 1800s and 1900s. For example, historians think that Queen Victoria of England (who ruled from 1837 to 1901) was a carrier of hemophilia B and passed it on to at least three of her nine children.

Of course, being a monarch isn’t actually a risk factor for hemophilia B. A person’s biological sex and family history are the main risk factors for hemophilia B.

What Is Hemophilia B?

Hemophilia B is a bleeding disorder in which the blood doesn’t clot properly. Some people develop hemophilia B due to genetic changes that occur randomly. Like hemophilia A and other types of hemophilia, hemophilia B is most often inherited from parents.

The biggest risk factors for developing hemophilia B are having a family history of the condition and being male. This is because of how the genetic change that causes hemophilia B is passed down from parent to child.

Hemophilia B goes by many names. It was originally called Christmas disease — named for the person in whom the disease was first diagnosed in the 1950s. Some countries, such as the United Kingdom and Australia, use the spelling “haemophilia B” for the same condition.

Hemophilia B is also called factor IX (9) deficiency, which refers to its cause — a lack of the clotting factor known as factor IX.

What Are the Symptoms of Hemophilia B?

People whose blood contains less factor IX may bleed longer and more often than others after an injury or medical procedure. People with more severe hemophilia B may also experience spontaneous bleeding episodes, or times when they bleed for no clear reason.

Hemophilia B is classified by the percentage of factor IX in a person’s blood. Normal plasma levels for people without hemophilia are between 50 percent and 150 percent.

Signs of mild hemophilia B — defined as having 6 percent to 49 percent of factor IX — include:

• Longer than usual bleeding episodes after injury, surgery, or trauma
• Heavy menstrual periods
• Hemorrhage (bleeding) during childbirth

Signs of moderate hemophilia B — 1 percent to 5 percent of factor IX — include:

• Bruising
• Prolonged or unusual bleeding episodes after injury, surgery, or trauma
• Spontaneous bleeding episodes

Signs of severe hemophilia B — less than 1 percent of factor IX — include:

• Bleeding episodes after minor injuries
• Frequent spontaneous bleeding episodes
• Hematoma (a mass of blood under the skin)
• Joint bleeds (the area looks bruised and feels warm)
• Breathing problems, if there is bleeding in the throat or chest

Babies with severe hemophilia B may learn to crawl and walk later than those without the condition. This may be due to painful joints or muscles or having fewer opportunities for free movement and floor play.

How Common Is Hemophilia B?

It’s hard to know how many people have hemophilia B. People with mild types of hemophilia B may not be aware of their condition.

A study released in 2020 looked at data from U.S. hemophilia treatment centers (HTCs). Data collected between 2012 and 2018 was used to estimate the number of U.S. males living with hemophilia. The researchers found that 3.7 of 100,000 males had hemophilia B.

However, the actual rates are likely higher. The study didn’t include females or the estimated 20 percent of people who were treated outside of HTCs.

Which Races or Ethnicities Are More Likely To Have Hemophilia B?

Hemophilia B can affect people of any race or ethnicity. Research is limited on whether the condition is more common among people of particular races or ethnicities.

The 2020 study compared the overall prevalence (number of people affected) of hemophilia among Hispanic, Black, and non-Hispanic white males in the U.S. The study didn’t state whether hemophilia B, specifically, was more or less prevalent within these groups.

Overall, the prevalence of all types of hemophilia was found to be:

• 15.1 per 100,000 for white males
• 12.4 per 100,000 for Black males
• 12.4 per 100,000 for Hispanic males

The study suggests race and ethnicity may play a role in the prevalence of hemophilia.

However, citing this study, The Coalition for Hemophilia posted, “As far as we know, the incidence of hemophilia is the same regardless of race or ethnicity. That is, everyone has the same chance of being born with hemophilia. The difference comes from the risk of death for the group. Blacks and Hispanics tend to live shorter lives than whites in the United States.”

Other research has focused on the effect of hemophilia on different racial and ethnic groups. One small study found that, among males ages 13 to 25 with hemophilia, nonwhite participants were more likely to develop inhibitors.

Inhibitors are antibodies produced by the immune system to attack infused clotting factor concentrates. Inhibitor development can make standard treatment regimens less effective.

More research is needed to understand whether hemophilia B affects some racial and ethnic groups more than others, and why that may happen.

Which Sex Is More Likely To Have Hemophilia B?

Hemophilia B is more common in males because of a change in chromosomes called sex-linked recessive inheritance.

The harmful mutation (change) in the factor IX gene — called the F9 mutation — is located on the X chromosome. Biological males inherit only one X chromosome from their mother, while biological females inherit one from each parent.

Biological males have one Y chromosome and one X chromosome. If a mother passes on the F9 mutation on the X chromosome to a male child, they will have hemophilia B. This is because they have no other healthy X chromosome that can override the mutation.

Biological females have two X chromosomes. This means that to develop hemophilia B, they must inherit the F9 mutation from both parents. Biological males are more likely to have hemophilia than females because they only need to inherit one affected X chromosome.

Biological females who inherit just one copy of the F9 mutation may be hemophilia B carriers. In other words, they don’t have hemophilia B, but they can pass it on to their children.

People with only one F9 gene mutation can also have bleeding symptoms. In those cases, they may need care similar to people with mild or moderate hemophilia.

One study found that about 24 percent of people with mild hemophilia B are female. However, females made up less than 1 percent of those with moderate or severe hemophilia B.

When Does Hemophilia B Usually Develop?

Hemophilia B is usually diagnosed in childhood. Severe hemophilia is usually diagnosed earlier because symptoms appear sooner than they do in mild cases.

The average age of hemophilia diagnosis depends on how severe the condition is:

• Severe hemophilia B is usually diagnosed by age 2.
• Moderate hemophilia B is usually diagnosed by age 6.
• Mild hemophilia B may not be diagnosed until later in life, often after an injury or surgery.

According to one study, the average age of males living with hemophilia in the U.S. is about 27.9 years. In contrast, the average age of females living with hemophilia is 31.4 years.

With improved hemophilia treatments and life expectancy, you may think that the average age should be closer to that of the general population in the United States — 39.2 years. However, the 1980s introduction of HIV and hepatitis C into the blood supply resulted in the deaths of many people with hemophilia.

Can You Reduce Your Risk of Hemophilia B?

Hemophilia B is usually inherited from parents. You can’t change the genetic mutation that causes hemophilia B.

Genetic tests can look for the mutations that cause hemophilia B. Genetic counseling can help you better understand your reproductive options and your family’s risk of developing hemophilia B.

Although you can’t reduce your risk of developing the condition, there are treatment options available. Hemophilia treatment can reduce your bleeding risk and help improve your overall health and quality of life.

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